Tuning system



Jan. 9, 1940. E. w. FORSTROM 2,186,828

TUNING SYSTEM Filed June 25, 1937 IYWVETfitOI": Edwar'd WFOF strom,

H is Attorney.

Patented Jan. 9, 1940 UNITED STATES TUNING SYSTEM Edward W. Forstrom, Stratford,

to General Electric Company,

New York Conn, assignor a corporation of Y Application June 25, 1937, Serial No. 150,389

4 Claims.

into radio receivers and which is well adapted for cooperation with dials having longitudinal scales. A further object of my invention is to provide such means which are motor driven and which, at the same time, are well-adapted to be driven by hand.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken with the accompanying. drawing, in which Fig. 1 represents an embodiment of my invention and Figs. 2, 3, and 4 represent details thereof.

Referring to Fig. 1 of the drawing, I have shown therein a tuning element I of a high frequency receiver such, for example, as is commonly employed for radio reception. .This element, in the form shown in the'drawing, may be the ordinary tuning condenser, or assembly of tuning condensers, of such receivers. The rotor of this condenser is mounted upon a shaft 2, which is provided with a pulley 3. The pulley 3 is driven by means of a cable 4, .the opposite ends 9 of which are attached to the respective ends of a somewhat elongated carriage, or rider 5. The carriage 5 is arranged for longitudinal movement behind the panel of the radio receiver, upon which may be mounted a dial 6, and it is provided with an index carrying arm 1 having a number of pointers, or indices 8 arranged thereon to cooperate with the scales which are provided upon the dial.

To provide for this longitudinal reciprocation 5 of the rider 5, it is arranged to slide upon a rail -lfzbeneath and parallel with which, is mounted a screw 9. This screw is provided with a split nut III, which is clamped between two members ll attached to the rider 5. These members II have a certain resilience tending to bear the opposite members of the split nut firmly against the screw. Thus as the screw is rotated, the split nut travels along it, causing the rider to slide along the rail 8.

It will be noticed that the rider 5 comprises, 5 at its right end, a strip of metal 5', which is bent around the rail and turned downward, the lower end being ben u backward to form afoot 2. The back edge of this foot bears against a member i3, only a fragment of which is shown, but which may comprise the chassis of the radio receiver. A similar member 5 may, of course, be provided at the opposite end of the rider, but this member, for simplicity of the drawing, is not shown in full.

These members 5 are connected together by one or more longitudinal members to form the rider 5. In the form of the invention shown in the drawing, the screw 9 is arranged to be driven by means of a motor I 4, the shaft of which is provided with a pulley I 5, which, in turn, is belted to a pulley I6, mounted upon the screw 9.

It is also arranged to be driven by means of a bevel gear l6 mounted on the opposite end of the screw the latter of which cooperates with, but is normally disengaged from bevel gear $6". This latter gear is preferably integral with a somewhat elongated toothed gear II which cooperates with a gear l8 mounted on the shaft of knob IS. The shaft of knob I9 is also provid ed with a disk I9" which, when the knob is pressed inwardly by the operator, engages the shoulder 19" formed on bevel gear 16" and presses that gear into engagement with bevel gear [6. Upon rotation of the knob the bevel gears are now driven due to'the meshing of gears I1 and I8 thereby rotating the screw and driving the carriage or rider 5. Upon release of the knob, rotation of the screw by the motor causes the bevel gears to disengage.

In practice the bevel gear it may suitably comprise a conical leather surface and the gear It" may comprise a die cast member having a conical knurled surface to cooperate therewith.

The motor I4 is connected to be controlled by a number of switches which are, operated by 5 means of a number of push buttons or keys, five of which, ll, l8, I9, 20, and 2| are shown on the drawing. The push buttons l1, l8, and [9 are. provided for purposes, later to be indicated and bear appropriate legends Motor, "Ofi, and Manual on the drawing. Push buttons 20 and 2|, and others, which may be incorporated in the same assembly, are provided to effect selective tuning of the receiver to desired frequencies,

and may, if desired, bear legends corresponding left hand position, as

to stations operating on those frequencies. That is, each of these buttons 28, El and-so forth corresponds to a particular broadcasting station, the connections being such that in response to operation of any of these buttons, the receiver is automatically tuned to the frequency at which the desired station operates. I

These buttons are all of similar construction,

comprising strips of metal 22 mounted within slots in two parallel members 23 and 23. The back ends of these members 22 are bifurcated,

one leg of the bifurcated portion being provided with a spring 26, one end of which bears against in the position shown in t e drawing, this locking member engages the right hand notch 25 of keys l8, l9 and 21 and the left hand notch 25 vof key 2%, the latter key having been pressed in- .26. engaging the left ward, in which position it is locked by member hand notch 25. If key 25 be now pressed inwardly, or any of the other keys except key H, the locking member 25 is raised as it rides from one notch of key i i to the other, and, when it is inits raised position, key 2b is released. It will thus be seen keys, except key its operated position butis returned to the normal position when any other key is operated. Key l1, however, when operatedlreturns to the normal position upon being released by the operator, and its operation does not release the other keys.

I condenser shaft. -This the condenser shaft whereby,

the slots at positions Keys 20 and 2E and the otherkeys correspond ing to frequencies to be selected, when in their inner position, engage contacts 28, 29, etc. respectively. These contacts are connected to stationary contacts 28' and 2s, respectively, of a commutator arrangemenhithle movable contact carrying arm 34 of which is mounted upon the commutator comprises a plate having a plurality of semi-circular, concentric slots in which the various contacts 28', 29' are mounted. The movable contact comprises a conducting member, the lower portionpf which is indicated at 3|. This contact is carried by a non-conducting member 32, pivotally supported between two ears 33 of the arm 34 mounted upon as the condenser rotates, thearm swings over the commutator and its contact 3| engages the different contacts 28", and 29 mounted in the slots of the plateau. V

ThecontactsiB', and 29 etc. are positioned in such that, when engaged by the movable contact 3!, the receiver is in accurate resonance at the frequency corresponding to the key operated. Since these frequencies may be comparatively close together in the frequency spectrum, the corresponding contacts, may necessarily be in closely spaced angular positions about the shaft of the condenser. For this reason the plurality of slots is provided and the contacts positioned in the different slots so that they may be placed in close, angular position,

even though the contacts and the securing means therefore may be'relatively large. 1

- The oppositeencl of the shaft-of the condenser with the exception 31 engages the stationary contact 23',

that any of thel'i, when operated, is lockedin is provided with a pair of oppositely extending arms EE'WhlCh, at the limits oftheir movement, engage the movable element 38 of a reversing switch 3i. This switch is connected in the field circuit of .the motor US, the connections being such that when the motor is operated, itfdrives sponseto operation of keys 2!), 2 i, etc., means are provided to stop the condenser, when the contact 29, etc,

corresponding to the station selected, This means comprises a relay 33 having an armature 39, whichloperates a plurality of contacts 40, ii, and and which, when in its attractedposition', extends into the path of movement of cars on the pulley iii, which is mounted on the motor shaft. These ears thus engage the arma- The winding of this relay is connected in circuit with the operated push button, or key, and with the corresponding contact or the commutator so. This circuit extends from ground, which may be the chassis of the radio receiver, through a suitable source of operating potential d3, winding of the relay 3%, member 23 of the opposite direction until the opl posits. arm 35 engages the element 36,thereby ture' 3b, which causes the stopping of the pulley key assembly, operated key, as, for example, key

26 as shown on the drawing, contact 28, 29, etc. of the operated key, stationary contact 2s, 29' of the commutator, movable contact '3! and thence to ground.

Relay 38, by means of its contacts 42, also con trols the circuit of the motor, this circuit, extending from one side of a suitable source of operating potential represented by conductors 50, thence through the motor, conductor 5!, contacts 52 of key I9,'contacts 53 ofkeyl8, and thence through contacts 42 to the other side of the source. One of the contacts ll of the relay is connected to ground, the other of these con tacts being connected through contacts 54 of key 59 to the automatic frequency control bus of the receiver. This automatic frequency control bus is the conductorof the receiver which is utilized to supply control potential to the automatic frequency control means of the oscillator. When this conductor is grounded, the automatic frequency control means is, of course, disabled.

One of the contacts 46 of the relay is also corresponding to button 20, this button being shown'in its operated position. The circuit of the relay previousl'yitraced is closed. throughzthe stationary contacts 23 and 28. The relay armature is therefore attracted and at its contact 42 deenergizes the motor, at its contacts 41 disconnects the automatic frequency control conductor from ground, thereby permitting the automatic frequency control device to function normally,

and at contacts 40 removes the ground connection from the silent tuning conductor of the re- 5 ceiver. Since its armature 39 is engaged by one of the cars 43 of the pulley l5, the condenser is stopped in the position corresponding to the desired frequency. The receiver is therefore in condition for reception of signals on the carrier frequency corresponding to key 20.

Wereit now desired to tune the receiver to a different frequency, as, for example, the frequency to which key 2| corresponds, this key may be operated to its inner position. In passing to ,1 its inner position push button 2i raises locking member 26, thereby releasing button 20, which, in turn, opens the circuit of relay 38 at contact 28. This relay becomes deenergized and its armature moves to the right, thereby permitting the .m pulley l5 again to be driven by the motor. At its contacts 42 the relay. closes the motor circuit, thereby causing the motor to start its rotation. At its contacts 4| it grounds the automatic frequency control conductor and at its contacts 40,

u it grounds the silent tuning conductor, thus silencing the receiver. The motor now continues to drive the condenser until contact 3! engages contact 29, which, in turn, again energizes relay 38. This relay now again stops the condenser go and opens its contacts 40, M and 12. The re ceiver now operates normally at the new frequency.

It is frequently desirable to tune the receiver by hand, that is, by operating the tuning control knob Hi. This may occur when it is desired to tune the receiver to a frequency for which no key 20, 2! is provided. This may be effected by pressing push button l9 which bears the legend Manual. Pressing this button, of course, re-

leases any other button which may previously have been pressed and opens the circuit of the motor at contacts 52. At contacts 55 it opens the silent tuning conductor, thus permitting normal response from the outputof the receiver.

45 At contact 54 it opens the connection of the automatic frequency control bus to ground. The receiver is now in condition to be tuned manually as by means of knob 19.

It may happen, however, that the index 8 at the beginning of manual operation, is at one end of the scale, whereas the position corresponding to the frequency of the desired station is at the opposite end of the scale. Accordingly, the operator may desire the assistance of the motor in tuning the condenser over this wide range. This he may obtain by pressing button H, which bears the legend Motor. The sole function of this button is to close the motor circuit only during the time when the button is pressed. Accordingly by pressing this"Motor button, the motor is energized and the tuning condenser driven thereby until the index reaches the position on the dial, approximately corresponding to the desired frequency. The operator may then release the Motor button and complete the tuning operation by rotation of the knob I9.

When it is desired to turn the receiver off, the operator presses the Off button Hi. This key, when pressed, remains locked in its inner position and, by means of its contacts 53, opens the motor circuit. Similarly, by means of its contacts 6!, it opens the energizing circuit of the receiver.

Fig. 2 shows in detail the member 32.

It Will 5 be seen that it comprises a pair of arbor-s 62 which may be pivoted in the ears 33 of the'arm 34. This member which is of non-conducting material, has a longitudinal slot in which the contact 3| is mounted, the member 32 having surfaces 3| inclined away from the edge of I member 3|, so that, when the member approaches a stationary contact of the commutator, these surfaces are first engaged, thereby causing the contact 3 I to ride smoothly upon the rounded end surface of the stationary contact. If the sta- 1o tionary contact be mounted in a slot above or below the pivot of the member 32, the member 32 rocks about its pivot correspondingly. This action tends to aid in the smooth and noiseless operation of the movable contact over the various 1 stationary contacts while at the same time assuring good electrical conduction between the engaged contacts. i

Fig. 3 is a detail showing a sectional view of plate 30 through one of the stationary contacts. Q It will be seen that these contacts comprise a screw-threaded member 33 having a head 64, which forms the contact. This member 63 engages a screw-threaded bore in a cooperating member or shank 65, a rubber bushing 66 being 3 clamped between the head 64 and the shank and within the slot, thereby to insulate the contact from plate 30.

With the equipment as thus far described, a considerable stress would be placed upon the In armature 39 of relay 38 each time that the tuning condenser is stopped by engagement of ears 43 with armature 39. This is undesirable and to avoid it, a suitable slip clutch, or brake, is provided, this mechanism being shown in detail in '5 Fig. 4.

Fig. 4 shows the shaft 61 of the motor on which the pulley I5 is mounted. This pulley is secured between two collars 68 and 69 on the shaft by means of spring pressure exerted by spring ll. 40 The pulley is attached to a disk 12 which, in turn, is provided with the ears 43, these members being free to rotate about the shaft. It will thus be seen that, when member 12 stops rotation by reason of an ear 43 engaging the armature 39, 5 the shaft 6'! may continue to rotate by reason of the inertia of the motor armature. This inertia of the armature is consumed in friction between the collar 68 and the left end of the pulley.

While I have shown a particular embodiment 5 of my invention, it will, of course, be understood that I do not wish to be limited thereto, since many modifications in the circuit and mechanical arrangements shown may be made and I contemplate, by the appended claims to cover any such 56 modifications as fall within the true spirit and scope of my invention.

WhatI claim as new and desire to secure by Letters Patent of the United States is:

1. In a tuning system including a tuning device w adapted to be adjusted to a plurality of positions,

a dial, an index cooperating with said dial, and a motor, a pulley connected to said tuning device, a reciprocating carriage,.a belt connecting the carriage and pulley, means to mount said index on said carriage, a screw, a screw-threaded member connected with said carriage and cooperating with said screw, means to drive said screw by said motor to adjust selectively and automatically said tuning device to certain predetermined positions, means to deenergize said motor, and manual means to drive said screw to adjust said tuning device to other predetermined positions, said manual means comprising a control shaft, a driven member connected to said screw, and a 7 driving member operatively associated with said control shaft and adapted to be :rotated thereby and to be pressed thereby into engagement with said driven member.

2. In a tuning system including a tuning device adapted to be adjusted to a plurality of predetermined positions, a dial having a longitudinal scale, as index cooperating with said dial and adapted to be adjusted correspondingly with said tuning device, a screw parallel with said dial, a rider cooperating with said screw, means to mount said index on said rider, a pulley connected, to said tuning device, a cable passing over said pulley and connected at its opposite extremities respectively to the corresponding opposite extremities of said rider, a motor to drive said crew and thereby to adjust said tuning device, means operatively associated with said timing device to reverse the direction of rotation of said motor when said index attains either end of said dial, means to deenergize said motor when said index and said tuning device arrive at certain of said predetermined positions, and manual means to rotate said screw thereby to adjust said index and said tuning device to others of said predetermined positions.

3. In a tuning system including a tuning device adapted to be adjusted to a plurality of positions, a dial, an index cooperating with said dial and adapted to be adjusted correspondingly with said tuning device, a pulley connected to said tuning device, a reciprocating carriage, a belt passing over said pulley and connected at its opposite extremities respectivelyv to the corresponding opposite extremities of, said carriage, means to mount said index on said carriage, a screw, a screw threaded member on said screw connected with said carriage, a motor to drive said screw thereby to drive said tuning device and said in.

deX, means operatively associated with said tuning device to deenergize said motor when said index and tuning device arrive at certain of said 4. In a receiver adapted to be tuned through a range of frequencies, a shaft, a tuning device having a rotor mounted on said shaft and adapted to he adjusted to a plurality of predeterminedpositions each corresponding to a respective frequency to which said receiver is tunable, a plurality of control keys corresponding respectively to certain of said positions, a screw, a rider cooperating therewith, means comprising a motor to rotate said screw alternately in opposite directions thereby to reciprocate said rider, means to connect said rider to said rotor of said tuning device to adjust said tuning device iii-accordance with'the movement of said rider, said last-named means comprising a pulley mounted on said shaft and a cable passing over said pulley and connected at its opposite extremities respectively-to the corresponding opposite extremities of said rider, means responsive to'operation of any of said keys to stop said tuning device in that one of said certain positions corresponding to the key,

operated, means to deenergized said motor, and manual means to rotate said screw thereby to ads just said tuning device to others of said predetermined positions. 

